Treatment of refractory ores.



J. FOYE, H. E. MOORE & R. BOYLE TREATMENT OF REFRACTORY ORBS.

APPLICATION FILED 111111.31, 1913.

Patented Oct. 13, 1914.

I I v STATES PATENT GFQFIOE.

JOHN TlOYE, HENRY EGBERT MOORE, AND ROBERT BOYLE, OF JOHAHNESBURG, TRANS- VAAL, SOUTH AFRICA, ASSIGNORS T0 REFRACTORY ORES, LIMITED, OF JOHANNES- BUEG, TBANSVAAL, SOUTH AFRICA. A

TREATMENT OF REFRACTORY ORES.

Specification of Letters Patent.

Patented 0017.13, 1914-.

Application filed March 31, 1913. Serial No. 758,016.

To all whom it may concern Be it known that/we, Jenn Fore, Hnsnr EGBEBX Moons, and Roemrr BOYLE, all Butish subjects, residing at (1) 108 Anderson street, Johannesburg, in the Province of the Transvaal, Union of South Africa, and (2 and Village Main Reef Gold Mining Company, Limited, J ohanncsbur aforesaid, have invented certain new an useful Improvements in the Treatment. of Refractory Ores, of which the following is a specification.

The present invention relates to the treatmcnt of refractory auriferous and other precious metal ores; the purpose being so to treat such ores as to render them readily amenable to the ordinary extraction methods, such as the cyanid process.

In the treatment according to the present invention, the ore is subjected to the action of an electric current in a solution of a soluble salt of sodium, potassium or ammonium, or' a mixture of any such salts, which are substantially non-solvents of gold, 6. g. the chlorids, sulfates .or nitrates. The anode is positioned in contact with or in proximityto the ore while the cathode is placed in the solution, imt out of contact with the ore.

Current passed between the electrodes, pro- -duesan acid solution -in the neighborhood of the anode and an alkaline solution in the neighborhoodof the cathode.' The ore is then separated from the liquid, whereupon,

ifthe period of treatment has been sufficient,

for which purpose the acid and alkaline so-' lutions are withdrawn separately from the 40'-,ore treatment vessel and then brought together in another vessel. A precipitate is .thereby' thrown down which appears to consist of the refractory constituents of the ore,

often much changed in character. Said preci itate may be treated for the extraction of any valuable metals it may contain. To ii'ect the precipitation it is necessary for thesolution to be neutral or alkaline, and if a this condition is not reached upon the ad pyrite by the oxy en liberated at the anode or to the added al ali (if any), may then be employed for further treatment.

The process may be made continuous, the separate acid and alkaline solutions being continuously withdrawn and fresh solut1on,- e. 9. that regenerated in the precipitation vessel,being continuously supplied.

Certain light constituents of ores, c. graphitic matter, are liberated from the ore during the treatment and float to the surface of the liquid. These may be removed by skimming or withdrawing the surface layer of the liquid. s

The strength of the solution may vary very considerably according to the nature of the ore under treatment, and the salts-employed. By way of example, it.may be.

mentioned that solutions of from 2% to 15% strength have becn.used with success and that the avera'g'e stnen h is-about 3%.

Owing to the comp icated nature of refractory ore it is impossible to give any definite statement of the chemical reactions which take place under-this process. When the electric currentpassesthrough the solu tion in the vat the solution is electrolized, its alkaline component forming in the-vicinity of the cathode and the acid component in the vicinity of the anode. It is-thc acid component, probably in the nascent state, which attacks the refractory constituent of the ore and for this reason it is necessary for the anode to be in contact with th ore. It appears that either the gold in the ore is unattacked or that it does not go into solution owing probably to the presence of the refractory constituents of the ore which do go into solution. Thus iron in the form of .pyrltes generally forms a part at least of the refractory constituent and the ferrous sulfate formed therefrom would prevent the gold from going into solution.

A form of apparatus for carrying out the process is shown diagrammatically in the ac companying drawing.

1 is a vat provided with a filter floor 2,

below which is a draw-oi? cock 3 for the acid solution. A draw-off cock 4 for the alkali solution "is positioned in the upper .part of the vnt.,-.An overflow launder 5 may be placed around-the rim of the 1%. and used for withdrawing the surface is' er of the liquid when necessary.

The anode 6 may consist ofanumber of ,Ca l'bOD. rods 7 dimming through the lowerpart'" of-the. vat an surrounded by a' layer of coke.

8. As illustrated in the drawing, the coke a lies on a filter mat'9. supported, by {grating 10. A further grating 11 covers the top-.o-f'

the coke and serves to kep-the'same in place and prevents the layer of ore 12 mixmg therewith. 'Ihe -cathod'e is conveniently formed to float at the'sur'facelof the, liquid. and may consistof carbon or metal rods'13 -or.plates 'secured'to a wooden framework 14.

"-the dischhrge. ate for'the'treated ore,

'Theremust e no electrical connectionbe- *1 modified in, various 'ways.- l hus, the vat. may be pjrovided with a separate chamber,

This construction assures the cathode being in proper contact with the solution, although the height of the latter in the yat may varyfrom' time "to time during the treatment of theore,

- 15 is the vessel in whichtheacidiand, 4 alkalixsolutions' are'Jre-combined-a's above described, and '16 is a puin for returning -the degenerated solution to t 'e'yat.

,117 is the inlet for fresh solutionand lo tween acid outlet 3 and alkali outlet .4. a 'The apparatus as illustrated} may be.

[with-which its lower part is incommunication. The acid draw-.ofi' cock maybe' positioned in the wall of' such chamber and.

thereby brought to the same height-'11s the alkali draw-oil cock, the uniform with.- draw'al oijthe two liquids being .thus facili'-. tatoi; -Inst-his:case, the filter mat-may be gosltlonedvertically t0 00V61' the o ening protee'tmgit -40 enabli 0a smal er mat' to "The" 'used, while from wear and facilitating its renewal." j" j f 1 As. an example-of the process it may, be assumed-that the materia "treated is a re fractory' ore 'havingits. "gold in association with =i rohpyrites.-, According-to. this inven- -tion'sfuchan ore; is placed in vat 1 chargedwith a suitable solution'"f0r instance of sov dium chlorid.-.;.-.Passage of-'the'current'be-- tweenanode 6 andcathode l3rtwillig lit up tween the rat-proper and the chem er, so,

the soluti-on and1 fehlorin-with-other ions n a= nascent "stat will be liberated at the anode. I t has b'eenfound that the iron is attacked by thenas'centfchlorin and. forms soluble'compounds therewith.

By dissolving the'iron out of the ore' the latter iS -Ieft' amenable to treatment for the extraction of the gold by any suitable pro-.

cess, e. 'way. The by-mixin' the solution containingthe iron and ClilOIIIl with the sodium solution which may -be withdrawn from the vicinity of the cathode The sodium will replace the iron lld sqdiu chlqrid is reiomed' Whafwe claim and desire to secure by Letters Patent i's:-'-

g; it.m ay be eyanided inthe usual sodium chlorid ,solution is regenerated- 4 1. The process of treating refractory ore for the purpose of rendering 1t amenable to ordinary extraction methods, which consists m subjectingthe ore in admixture with a solution of the' salt of an -alkaline metal,

which is substantially a non-solvent of gold,

to the passage of an electric current, where by the ac1d component ofthe solution sepg' farates'm proximity to the ore and the alka' line component away therefrom, and subsequently separating the ore and solution.

2. In apparatus for treating refractory ore for the purpose of rendering it-amenable to ordinary extraction methods, the combination of a'vat, a filter floortherein, a float a'daptedfto floatat the surface of solution in the vat, electric conductors thereonyand adapted to projectinto the.solution; an anode in the lower part of the vat,.and means fOI separately drawin ofi' solution from the tively.,

In testimony'whereof we afiixour signavacinities of the arm eand cathode respec- 

